The present invention relates to systems for lubricating high viscosity material in a pipeline. In particular the present invention relates to a pipeline lubrication system with a lubrication spool which can be positioned between flanged ends of first and second pipes to lubricate a plug flow of high viscosity material and which can be removed from the position between the first and second pipes without disturbing the integrity of the pipeline system.
Pump and pipeline systems are frequently used to convey high viscosity materials such as sludge and concrete over long distances. In these applications, sludge is generally defined as a high viscosity material which typically has no free flow characteristics. High viscosity materials are typically pumped through a pipeline in a plug flow. Pumping a plug flow of high viscosity material over a long distance through a pipeline requires a pump capable of producing high pumping pressures to overcome friction between the high viscosity material and the pipeline. The further the material has to be pumped through the pipeline, the greater the pressure that is required, and therefore the greater the horsepower requirements of the pump.
When pumped through a pipeline under pressure, a plug flow of material such as sludge releases liquids which form a film of lubricant around the flow. The lower the liquid content of the material being pumped, the less liquid available for lubrication. For this reason, dryer materials will experience more friction and will therefore require higher pumping pressures than are necessary to pump materials with higher liquid contents.
Typically, lubrication of a plug flow is necessary only when the material being pumped doesn't contain enough liquid to form a film of lubricant around the inner wall of the pipeline. Adding a layer of lubricant around a plug flow of these materials results in lower pumping pressures and increased capability of pumping the material greater distances at a given pressure.
With materials such as sludge, liquids may well have been intentionally removed prior to pumping. In these instances, it is not desirable to substantially increase the liquid content of the material being pumped in order to increase the material's pumpability. A number of pipeline lubrication systems have been developed to lubricate a flow of high viscosity material in a pipeline without substantially increasing the liquid content of the material. An example of such a pipeline lubrication system is disclosed in Coursen, U.S. Pat. No. 4,510,958. Coursen discloses an apparatus and method for injecting a lubricating liquid into a conduit around a flow of high viscosity material. The lubricant is injected through a slanted circumferential slot in the direction of the flow of the high viscosity material. Injecting the lubricant through the slanted circumferential slot in the direction of the material flow reduces resistance against the flow and also helps to prevent the high viscosity material from clogging the circumferential slot.
Although pipeline lubrication systems like the one disclosed in Coursen help increase the pumpability of high viscosity materials, they have significant disadvantages. One very important disadvantage of prior art lubrication systems is that, in order to remove the lubrication mechanism from the pipeline, the pipeline must be disassembled. Once disassembled, it is very difficult to reconnect adjacent pipe sections. Pipe sections are under extreme stress, and when disconnected, they frequently contract or otherwise shift to such an extent that they cannot be easily reconnected.